1. Field of the Invention
The invention relates to an equipment control system for equipment such as a refrigeration device for cooling a space to be cooled, a control device for controlling the refrigeration device, and a control program used in the control device.
2. Description of Related Art
A refrigeration device for cooling a space to be cooled such as a showcase installed in a store, such as a supermarket or a convenience store, has been widely used in the past. The space to be cooled for example indicates an inside of the showcase for displaying merchandises. At a cooling unit of such a cooling device, moisture in the air adheres as frost, and therefore, a defrosting operation is performed periodically in which the temperature within the space to be cooled is raised and the frost adhered to the refrigeration device is removed. Here, the frost adhered to the refrigeration device indicates, for example, the frost adhered to the cooling unit of the refrigeration device and the frost adhered to the wall surface inside the showcase. By periodically removing the frost adhered to the cooling device, a good cooling performance of the refrigeration device can be maintained.
It is common that the defrosting operation is performed from its start until a predetermined termination condition is met. Here, the termination condition is for example that the temperature within the space to be cooled reached a given temperature. Therefore, when the time required for the defrosting takes longer, it is considered that a larger amount of frost is adhered to the refrigeration device at the time of the defrosting.
In view of this, Japanese patent Laid-Open No. 5-272860 proposes a method to change start time of a present-round defrosting operation from scheduled start time in accordance with the time required for the last defrosting operation. In particular, if the last defrosting operation took a long time, it is considered that it has a tendency to have a large amount of adhered frost, and the start time for the present-round defrosting operation is advanced from the scheduled start time. Also, if the last defrosting operation took a short time, it is considered that it has a tendency to have a small amount of adhered frost, and the start time for the present-round defrosting operations is delayed.
However, the defrosting operation is started at certain frequencies, such as in the four-hour or six-hour interval, and therefore, there is an instance in which environmental conditions such as the in-store temperature and the in-store humidity at the time of the last defrosting operation may differ greatly from the environmental conditions at the time of the present-round defrosting operation. Here, the environmental conditions at the time of the defrosting operation are the conditions that affect the required time for the defrosting operation. For example, in a case of the showcase, the amount of adhered frost varies in accordance with the in-store temperature, the outdoor air temperature, the in-store humidity, and so on.
Therefore, in the method of Japanese patent Laid-Open No. 5-272860 in which the start time for the present-round defrosting operation is changed according to the time required for the last defrosting operation, there was a problem that the tendency prediction for the amount of adhered frost may not be accurate, and the start time for the present-round defrosting operation may not be appropriately changed from the scheduled start time when the environmental conditions at the time of the last defrosting operation differ greatly from the environmental conditions at the time of the present-round defrosting operation.
Thus, the present invention was made to solve such a problem and provides the equipment control system, the control device and the control program that can change the start time of the present-round defrosting operation appropriately even when environmental conditions at the time of the last defrosting operation differ greatly from the environmental conditions at the time of the present-round defrosting operation.